1. Field of the Invention
The present invention relates generally to circuitry, and more specifically to circuitry that senses a current.
2. Background
Portable electronic devices are becoming increasingly popular in the marketplace. Such portable devices often include a low power switch regulator, which includes power conversion circuitry and other mixed-signal circuitry. A variety of techniques have been employed to improve the performance of conventional switch regulators. A trend in the industry is to integrate the power conversion circuitry and the other mixed signal circuitry on the same substrate to improve efficiency. Current sensing is another technique that may be used to improve the performance of a switch regulator. For example, an integrated switch-mode converter of the switch regulator may be configured to sense a current of the portable electronic device. Several conventional current sensing techniques are available. However, each of these techniques has problems that may render the respective techniques inadequate and/or undesirable for at least some applications.
Many conventional techniques sense current by incorporating a serial resistor in the path of the current. For instance, a first conventional technique uses an off-chip resistor coupled in series with an inductor to sense the current of the inductor. However, this technique requires the entire current of the inductor to flow through the resistor. For this and other reasons, the first conventional technique is characterized by a relatively high power dissipation. Moreover, additional input/output (I/O) pins and board routing are needed for implementation of this technique.
In a second conventional technique, a resistor is coupled in series with a main power switch. The drain current of the main power switch flows through the resistor, enabling the drain current to be sensed. However, this technique is characterized by relatively low efficiency. For example, the resistor used in the second conventional technique needs to be large enough to provide sufficient swing for further analog signal processing.
What is needed is a system and method that addresses one or more of the aforementioned shortcomings of conventional current sensing techniques.
In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the leftmost digit(s) of a reference number identifies the drawing in which the reference number first appears.